1. Field of the Invention
The present invention relates to a mobile communication terminal having not only mobile phone functions but also at least a function of receiving digital terrestrial television broadcasting targeted to mobile communication terminals and a function of communicating with a network, such as a multifunctional (versatile) mobile phone. More specifically, the invention relates to operation check self-diagnosis of a digital terrestrial television broadcasting receiver of the mobile communication terminal. In the present invention, the “mobile phone functions” refer to wireless call and communication functions using a telephone network of various mobile communication terminals including mobile phones, personal handy-phone system (PHS) phones, and the like.
2. Description of the Related Art
In recent years, it has been proposed to incorporate into mobile communication terminals typified by mobile phones not only mobile phone functions but also at least a function of communicating with a network, such as a local area network (LAN) or a personal area network (PAN), and a function of receiving digital terrestrial television broadcasting targeted to mobile communication terminals in order to promote increases in user convenience, and the like.
Such a multifunctional and versatile mobile communication terminal is manufactured by modularizing the functions on a function-by-function basis and incorporating the module components having the functions into a case.
As for the above-mentioned digital terrestrial television broadcasting reception function, the module components must undergo operation check individually in the component manufacturing process, as a matter of course. Further, the module components must undergo operation check with the module components mounted or incorporated in a mobile communication terminal in the process of assembling mobile communication terminals, the process of shipping them, and the like.
Also, after shipped mobile communication terminals are provided to users, a situation where a radio wave is not received occurs in areas where it is difficult to receive broadcasting, reinforced concrete buildings, and places where radio waves of digital terrestrial television broadcasting are extremely weak or such radio waves do not reach the mobile communication terminals, such as a underground shopping center even if the users attempt to receive digital terrestrial television broadcasting. Poor reception generally creates dissatisfaction as well as anxiety to the users. Therefore, it is convenient to provide, when such a situation occurs, an operation check self-diagnosis that can be performed easily to determine whether the digital terrestrial television broadcasting reception function is operating normally.
For example, with regard to a wireless communication unit for ship, it has been proposed to perform operation check self-diagnosis of a transmission/reception section of the unit using a folding circuit, such as generally discussed in, for example, Japanese Unexamined Patent Application Publication No. 2003-218811 (Abstract, paragraphs [0022] to [0048], FIG. 1, etc.).
FIG. 7 shows a wireless communication unit 100 for ship disclosed in the above-mentioned Japanese Unexamined Patent Application Publication No. 2003-218811. The wireless communication unit 100 transmits or receives radio waves to or from other ships or seacoast stations via a satellite (not shown) and has a self-diagnosis function. For this reason, the wireless communication unit 100 includes a control circuit 101 that controls the entire wireless communication unit 100, a frequency converter 102, an RF section 103, and a local signal supply circuit 104 that functions as a part of the folding circuit.
The control circuit 101 includes a control section 105, a demodulator 106, and a modulator 107. The control section 105 performs activation or deactivation of a local signal oscillator 108 of the local signal supply circuit 104, control of gains of an automatic gain control amplifier (AGC) 109 and a power amplifier 110 of the RF section 103, and the like. Also, the control section 105 provides transmission data of a baseband signal to the modulator 107 and takes in demodulation data of a baseband signal demodulated and outputted by the demodulator 106.
In the RF section 103, a diplexer 112 connected to an antenna 111 includes a reception band-pass filter 112A having a pass frequency of 1.5 GHz and a transmission band-pass filter 112B having a pass frequency of 1.6 GHz.
An output signal of the reception band-pass filter 112A is inputted into the frequency converter 102 via an RF reception-type low-noise amplifier (LNA) 113, a band-pass filter 114 having a pass frequency of 1.5 GHz, and an automatic gain control amplifier 109. A transmission signal of the frequency converter 102 is inputted into the transmission band-pass filter 112B via the power amplifier 110.
The local signal supply circuit 104 is provided to perform self-diagnosis and is activated only when performing self-diagnosis. When performing self-diagnosis, the local signal oscillator 108 generates a local signal L of 0.1 GHz, and the generated local signal L is inputted into the input of the low-noise amplifier 113 via the filter circuit 115.
In the filter circuit 115, 116 is a stopping capacitor, and 117 and 118 represent choking coils for interrupting the local signal L.
When performing normal operation in which radio signals are transmitted or received, the local signal oscillator 108 is deactivated.
During such a period, a baseband signal of transmission data outputted from the control section 105 of the control circuit 101 is converted into an intermediate-frequency signal in the modulator 107. Subsequently, the intermediate-frequency signal is further converted into a signal of 1.6 GHz by the frequency converter 102. The signal of 1.6 GHz is power-amplified by the power amplifier 110 and then wirelessly transmitted from the antenna 111 via the diplexer 112 as a transmission signal Sd.
Also, a reception signal of 1.5 GHz of the antenna 111 is inputted into the low-noise amplifier 113 via the diplexer 112 and then inputted into the automatic gain control amplifier 109 via the low-noise amplifier 113 and band-pass filter 114. Then, the signal is amplified to given amplitude by the automatic gain control amplifier 109 and then provided to the frequency converter 102. The frequency converter 102 converts the above-mentioned reception signal of 1.5 GHz into an intermediate-frequency signal and provides the intermediate-frequency signal to the demodulator 106. The demodulator 106 demodulates the intermediate-frequency signal into a baseband signal, and demodulation data of the baseband signal is decoded in the control section 105.
On the other hand, when performing self-diagnosis, the control section 105 of the control circuit 101 activates the local signal oscillator 108, which brings the local signal oscillator 108 into an oscillation state—a state where a reception signal of the antenna 111 is not inputted.
Also, the control section 105 outputs a baseband signal of transmission data for self-diagnosis to the modulator 107.
Subsequently, the above-mentioned baseband signal of transmission data for self-diagnosis is modulated into an intermediate-frequency signal by the modulator 107. The intermediate-frequency signal is converted into a signal having given amplitude and 1.6 GHz by the frequency converter 102. The signal is passed through the power amplifier 110 and band-pass filter 112B and then leaked into the low-noise amplifier 113 via the band-pass filter 112A as a leak signal Se of 1.6 GHz.
At that time, the local signal L of 0.1 GHz of the local signal oscillator 108 is provided to the input of the low-noise amplifier 113 via the choking coil 118.
Subsequently, the leak signal Se of 1.6 GHz and the local signal L of 0.1 GHz are mixed using the input-output non-linear characteristic of the low-noise amplifier 113. Thus, a signal of 1.7 GHz and a signal Sm of 1.5 GHz, which is a frequency identical to that of the reception signal occur at the output of the low-noise amplifier 113.
Also, the signal of 1.7 GHz is blocked by the band-pass filter 114. Thus, the signal Sm that is 1.5 GHz identical to the frequency of the reception signal and can be used as a self-diagnosis signal is provided to the frequency converter 102 via the automatic gain control amplifier 109. Then, an intermediate-frequency signal of the signal Sm outputted from the frequency converter 102 is provided to the control circuit 101.
Subsequently, the control section 105 of the control circuit 101 compares demodulation data obtained by demodulating the above-mentioned intermediate-frequency signal (folded signal) of the signal Sm using the demodulator 106, with the transmitted original transmission data for self-diagnosis. Thus, the control section 105 determines whether the RF section 103 and the like are normal or abnormal. Thus, the control section 105 performs operation check self-diagnosis.
This type of mobile communication terminals, such as the above-mentioned multifunctional mobile phone, must undergo operation check of the digital terrestrial television broadcasting reception function included therein in the assembly process, shipping process, or the like.
In this case, in order to avoid an increase in cost of a mobile communication terminal due to an operation test as much as possible, it is desirable that the mobile communication terminal perform operation check self-diagnosis of the function of receiving digital terrestrial television broadcasting targeted to mobile communication terminals without using a test instrument dedicated to digital terrestrial television broadcasting, such as an OFDM test instrument.
Also, if a mobile communication terminal includes such a self-diagnosis function, it is possible to easily perform the above-mentioned operation check as to whether the digital terrestrial television broadcasting reception function is normally operating (i.e., whether there is or not a failure in a module component) in places where a radio wave of digital terrestrial television broadcasting is extremely weak or does not reach the mobile communication terminal, or the like, as described above, after the mobile communication terminal is provided to a user. A self-diagnosis function is convenient and provides an increase in, e.g., reliability of the communication device.
However, there has not been invented any configuration where this type of multifunctional mobile communication terminal performs self-diagnosis of an operation test of the included function of receiving digital terrestrial television broadcasting targeted to mobile communication terminals.
On the other hand, it can be said that the above-mentioned wireless communication unit 100 for ship shown in FIG. 7 has a configuration where an oscillator OSC necessary for self-diagnosis is added to a transmission block Ta and a reception block Ra originally necessary for communication, as shown in FIG. 8. The transmission block Ta is a circuit block extending from the modulator 107 to the band-pass filter 112B via the frequency converter 102 and power amplifier 110 in FIG. 7. The reception block Ra is a circuit block extending from the band-pass filter 112A to the frequency converter 102 via the low-noise amplifier 113, band-pass filter 114, and automatic gain control amplifier 109 in FIG. 7. The oscillator OSC is the local signal supply circuit 104 shown in FIG. 7.
The wireless communication unit 100 can self-diagnose whether the included function is running. However, the wireless communication unit 100 requires the oscillator OSC for self-diagnosis that is not necessary for call and communication, which are the original functions. For this reason, a special additional circuit component, such as the local signal oscillator 108, must be included in the wireless communication unit 100.
Also, in order for the oscillator OSC to accurately generate the local signal L of 0.1 GHz significantly distant from the original transmission frequency of 1.5 GHz of the wireless communication unit 100, the oscillator OSC must be actually formed on a PLL circuit that includes a voltage control-type oscillator using a quartz crystal vibrator, a frequency divider, a phase comparator, and the like, is large in circuit size and costly, occupies a large area of a substrate, and has a low frequency.
Therefore, the wireless communication unit 100 including the oscillator and having the self-diagnosis function is made up of many components and is complicated, costly, and large in size.
It is also conceivable to use an external adaptor for the wireless communication unit 100 as the oscillator OSC. In this case, the wireless communication unit 100 becomes low-cost and small accordingly. However, the oscillator block OSC adaptor must be always prepared and a power supply for this adaptor is required independently. For this reason, the whole unit including the oscillator OSC adaptor becomes large in size and costly unexpectedly. Further, self-diagnosis can be performed only in places where power supply for the adaptor can be obtained, or the like. That is, in not all places can self-diagnosis be performed.
Also, the wireless communication unit 100 performs self-diagnosis by generating the signal Sm having a frequency that is the difference between the leak signal Se and local signal L, i.e., the signal Sm of 1.5 GHz identical to the frequency of the reception signal due to internal modulation distortion between the leak signal Se of 1.6 GHz of transmission data for self-diagnosis and the local signal L of 0.1 GHz using the non-linear characteristic of the low-noise amplifier 113. In this case, the original leak signal Se strongly remains at 1.6 GHz near the signal Sm of 1.5 GHz. As such, the leak signal Se may interfere with reception.
It is also conceivable to incorporate an additional circuit, such as an oscillator similar to the local signal oscillator 108, into this type of multifunctional mobile communication terminal so that the mobile communication terminal performs operation check self-diagnosis of the included digital terrestrial television broadcasting reception function as in the wireless communication unit 100. However, dosing so requires a special additional circuit component for self-diagnosis, resulting in upsizing of the mobile communication terminal, i.e., failing to meet a downsizing demand. Further, the cost is significantly increased.
Also, it is conceivable to form a special additional circuit component for self-diagnosis in an adaptor independent of the mobile communication terminal. In this case, the whole unit including the adaptor becomes complicated, costly, and larger in size unexpectedly. Further, it is inconvenient to carry the adaptor together with the mobile communication terminal. Furthermore, self-diagnosis can be performed only in places where power supply for the adaptor can be obtained. Hence, there is a problem with regard to restricted places where self-diagnosis cannot be performed.
Also, there is a problem that in any of the case where the above-mentioned special additional circuit component for self-diagnosis is incorporated into the mobile communication terminal and the case where such an additional circuit component is formed as an adaptor, the above-mentioned reception interference occurs.